Diethylstilbestrol (DES) was taken during pregnancy by an estimated four million women in the United States, from the late 1940's until 1971. Cancer and other health risks in the offspring have been associated with the maternal ingestion of DES, but the risks for the mothers have not been clarified. An elevated breast cancer risk has been reported, especially in women after age 50, and 20 years or more after exposure. A health survey is proposed to assess breast cancer and other health risks in a unique cohort of previously identified DES-exposed and control women. The subjects of this study participated in a double-blind trial of the use of DES during pregnancy in 1951-52. All participants received a placebo or DES according to a standard dosage schedule. Baseline health data have been obtained up to 1980 on 80% of these women. In order to monitor any excess of disease in the exposed population, it is planned to complete a health questionnaire for all subjects by December, 1987. Medical records of hospitalizations and pathology reports for tissues removed at surgery will be obtained. In the case of tumors related to the genital tract (breast, ovary, endometrium, and cervix), pathology slides will also be obtained for review and verification. The findings between the exposed and unexposed will be compared, and also evaluated in relation to the general U.S. experience. The results of this controlled study can lead to new findings and health surveillance recommendations for the mothers who took DES during pregnancy.